The present invention relates to a brazing fin stock for use in an aluminum base alloy heat exchanger, and more particularly to a brazing fin stock having a sacrificial anode effect so that the tube- or plate-shaped fluid passage member of the heat exchanger is protected from corrosion.
Air condensers or evaporators for car air conditioners have been normally constructed by vacuum soldering fin members made of brazing sheets to main tube members through which a coolant flows and which have been formed from a porous aluminum or Al-Mn type alloy by the process of extrusion. Conventionally, the brazing sheet for the fin member is fabricated from a core alloy of 3003 aluminum alloy or 6951 aluminum alloy and a cladding alloy of Al-Si-Mg type alloy.
In use such a conventional heat exchanger is subjected to considerable corrosion damage when the air-cooled side of the heat exchanger is exposed to a severely corrosive environment, and, thus the applications of such conventional heat exchangers are limited to a narrow range. The corrosion encountered with conventional heat exchangers is illustrated by FIG. 1. When the heat exchanger wherein a main tube member 1 and a fin member 2 are joined to each other at a fillet portion 3 by means of vacuum soldering is fabricated from the conventional materials, the fillet portion 3 becomes more cathodic and a corrosion-current flows in the direction of the arrow so that pitting corrosion 4 occurs in the main tube member 1.